The present invention relates to the construction of an electrode assembly for an implantable medical device such as a pacemaker or defibrillator, which enables it to be implanted, then easily explanted when necessary in a manner not previously known.
While the present invention will be described in a specific manner as being applicable to a pacemaker, it will be understood that the invention is applicable to any other type of implantable medical device intended to stimulate body tissue. Modem pacemakers monitor the activity of a heart and provide a stimulation pulse in the absence of normal heart activity. Advantageously, such devices are relatively small, lightweight and implantable. In order to sense and stimulate the heart, however, such pacemakers must be used with a pacemaker lead, an electrical conductor that carries electrical signals between the heart and the pacemaker. The pacemaker lead can be inserted into the heart transvenously through a relatively simple and well-known surgical procedure.
Lead extraction is required when an infection occurs and at times when products are upgraded or replaced. When infected leads must be removed, physicians have shown a desire to remove uninfected leads to rid the venous system and right ventricle of unnecessary hardware Current lead extraction techniques have proven adequate but can be time-consuming. The technique of extraction runs a high risk of lead separation. The locking stylet method can run the risk of jamming midway in the lead and is sensitive to inner diameters of leads. Such an occurrence can result in ineffective lead removal or lead separation. The laser extraction method is expensive and not readily available.
For some extractions, removal of the lead body is necessary and extraction of the distal tip is exceedingly difficult because of fibrosis on the myocardium to the tines. Tines are used to fixate and stabilize passive fixation leads. If the distal tip (including tines) were detached, the lead extraction could continue at a low risk.
A number of patents are somewhat definitive of the prior art in this regard. Connector appliances are known for easily and rapidly connecting a lead to an electromedical device, which may be implanted in the body of a recipient and also for disconnecting the lead. Typical of such appliances are U.S. Pat. No. 5,885,280 to Nettekoven et al. for xe2x80x9cElectrosurgical Electrode Connectorxe2x80x9d, U.S. Pat. No. 5,807,144 to Sivard for xe2x80x9cDevice for Affixing a Lead Connector to an Implantable Stimulatorxe2x80x9d, U.S. Pat. No. 5,545,188 to Bradshaw et al. for xe2x80x9cCardiac Pacemaker with Collet-Type Lead Connectorxe2x80x9d, and U.S. Pat. No. 5,489,225 to Julian for xe2x80x9cElectrical Terminal with a Collet Grip for a Defibrillatorxe2x80x9d.
More closely akin the present invention are patents, which disclose apparatus for implanting and explanting a distal lead to and from a desired body site. Typical of this group of patents are U.S. Pat. No. 5,261,419 to Osypka for xe2x80x9cCardiac Pacemaker Leadxe2x80x9d and U.S. Pat. No. 5,207,683 to Goode et al. for xe2x80x9cApparatus for Removing an Elongated Structure Implanted in Biological Tissuexe2x80x9d.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
The present invention relates to an electrode assembly for a body implantable lead provided for the delivery of stimulation energy to a desired body site and includes a tip electrode having a face adapted for positioning at least adjacent the desired body site and a longitudinally extending axially aligned weld electrode engageably receiving a distal end of an electrical conductor at a proximal end. The electrical conductor is a coiled wire strand with an inner peripheral surface for fitting reception on an outer peripheral surface of the weld electrode. A connector member includes a fastener having an enlarged head and a threaded shank, the weld electrode includes an integral weld sleeve with an annular locking tab engageable with the enlarged head to prevent longitudinal movement while permitting rotational movement. The weld electrode has an internal bore for receiving an elongated stylet selectively engageable therewith for implanting the electrode assembly at a desired body site and for explanting the electrode assembly from that body site. The tip electrode includes an integral attachment sleeve having an outer peripheral surface extending in a direction away from the face thereof and having a longitudinally extending tapped bore for threaded engagement with the threaded shank of the connector member. The weld sleeve and the attachment sleeve are mutually stepped to prevent their relative rotation when in the locked position. An insulative sheath is fittingly received on the outer peripheral surface of the attachment sleeve and includes a plurality of circumferentially spaced, radially outwardly projecting integral tines.
This invention, then, concerns a lead that has a removable distal electrode which gives the lead the ability to be removed without traumatic surgery. This translates into reduced money and time for the lead extraction procedure. The mechanism is designed for a passive fixation electrode but it can easily be incorporated into an active fixation lead.
The invention is activated by a stylet that has a driver mechanism. In this embodiment, the driver mechanism is a flat blade screwdriver. Standard ball-tip stylets can and are used for implanting the lead and do not affect or activate the driver mechanism.
When a physician has determined that a lead has to be extracted, the first procedure is to pull on the lead to determine whether it can be removed without further surgical procedures. If that is unsuccessful, the physician has the option to detach the distal tip and remove the lead, leaving the tip in the fibrotic growth. This results in shorter time in the operating room and increased safety for the patient. The doctor activates the mechanism by inserting the screwdriver stylet into the lead and advancing the stylet to the most distal position. When that position is reached, the physician then rotates the stylet counterclockwise as if removing a bolt. The stylet engages into the slot of the detachable tip mechanism and further rotation of the stylet results in the tip detaching. The physician then easily extracts the lead.
It is a feature of the present invention to provide the construction of an electrode assembly for an implantable medical device such as a pacemaker or defibrillator, which enables it to be implanted, then easily explanted when necessary.
It is a further feature of the present invention to provide a surgeon with the option, in one instance, of extracting both the lead and the tip electrode if possible without undue harm to the surrounding tissue and, in another instance, of extracting only the lead, leaving the tip electrode in the fibrotic growth which impedes its removal.
Still a further feature of the present invention is to provide such an electrode assembly with a highly removable tip electrode for safer and less costly lead explants.
Yet a further feature of the present invention is to provide such an electrode assembly with a construction which activates with a special driver stylet.
A still further feature of the present invention is to provide such an electrode assembly with a lead, which becomes isodiametric for easy removal.
Yet another further feature of the present invention is to provide such an electrode assembly with a construction which handles like a standard RV lead at implant.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.